The present invention relates to transparent molds, which are made of selected polyamide molding materials, the physical properties of which, in particular the transparency and the dynamic resistance, are superior to polycarbonate. The molds of the invention achieve in part multiple times more bending cycles at higher stress than polycarbonate without damaging the molded part.
Transparent molds made of polyamide or polycarbonate are known from the state of the art. For special applications, such as e.g. glass for frameless glasses, polycarbonate is normally used, wherein the glass has e.g. screws for connection with the earpiece and the nose bridge.
However, mechanical stress fractures, which can lead to breaks in the lens in the case of a dynamic bending load, develop at these connections in particular in the case of polycarbonate.
For the production of frameless glasses, numerous constructions are described in literature for the fastening of the earpieces and the nose bridge to the lens. In all cases, this is performed by means of e.g. bore holes, tapped holes, blind holes, bushings or grooves in the lens and fixation with e.g. screws, pins, bolts, clamping devices or nylon threads.
EP 1 630 590 describes a fastening of glass lenses and a method for repairing lenses and glasses. It can also be applied to plastic lenses, wherein the lenses can e.g. be made of polycarbonate, acrylic resin, urethane resin and polyamide. More exact information on the types of polyamide that can be used was not provided. Moreover, properties, which the polyamide must fulfill in order to be suitable as a lens for frameless glasses, are not named. An example of frameless glasses is shown in a unfamiliar drawing.
Such frameless glass constructions with fastening elements such as earpieces, bridge or nose support fixed on the lens place very high demands on the dynamic capacity of the transparent material. As know from U.S. Pat. No. 7,014,315, these requirements cannot be fulfilled in a satisfactory manner by polycarbonate, PMMA, CR39 (duroplast based on diethylene glycol (bis)allyl carbonate) and glass.
The object of the present invention is thus to develop transparent molds made of polyamide molding materials, which have a low tendency to form mechanical stress fractures in the case of a dynamic load.
This object is solved with the transparent mold with the characteristics of claim 1. The dependent claims represent advantageous embodiments. Applications described herein.
In accordance with the invention, a transparent mold is suggested, which is formed from a polyamide molding material, which has at least one polyamide and/or blends of such with a light transmission (transparence) of at least 75% at a layer thickness of 2 mm, measured as per ASTM D 1003 as well as an alternating bend resistance with fixation of at least 60,000 measurement cycles, measured as per ISO 178 with a special test piece. The at least one polyamide is formed from at least one diamine selected from the group of hexamethylene diamine (HMDA), bis-(4-amino-3-methylcyclohexyl)methane (MACM) and/or bis-(4-amino-cyclohexyl)methane (PACM) as well as from at least one dicarboxylic acid selected from the group of isophthalic acid (IPS), terephthalic acid (TPS) and/or dodecanedioic acid (DDS) or from the aforementioned diamines and dicarboxylic acids in combination with lactams and/or α-/ω-amino acids.
Surprisingly, a combination of monomers was found that allows the production of the polyamide molding materials, from which transparent molds can be formed, which fulfill the set objective. It was particularly surprising that the molds, e.g. when used as a lens, reach at least 60,000 bend cycles despite weakening through damage to the material structure of the lens by e.g. a bore hole, tapped hole, blind hole, bushing, groove, sawed, milled or ground edges.
The polyamide molding materials contained in the transparent molds tolerate constructive damage to the material structure, which was only unsatisfactorily possible with transparent substances up to now. The excellent chemical resistance known from polyamide is simultaneously retained.
The transparent molds according to the invention also have good heat resistance, rigidity and hardness.
The molds show a high dynamic load capacity and very high light transmission and are particularly suitable for producing correcting and non-correcting lenses, which are preferably used in frameless glasses.
In an advantageous variant, the at least one polyamide and/or blends of polyamides is formed from approx. 100 mol-% DDS as dicarboxylic acid and relating to 100 mol-% diamine from                a) 20 to 100 mol-% MACM and        b) 80 to 0 mol-% PACM and/or        c) 80 to 0 mol-% HMDA.        
In particular, the polyamide molding material is a polyamide made of MACM and DDS.
As an alternative, it is advantageous if the at least one polyamide and/or polyamide blends is formed from approx. 100 mol-% HMDA as diamine and relating to 100 mol-% dicarboxylic acid from                a) 60 to 100 mol-% IPS and        b) 40 to 0 mol-% TPS and/or        c) 40 to 0 mol-% DDS.        
Another advantageous variant provides that the at least one polyamide and/or polyamide blends is formed from approx. 100 mol-% DDS as dicarboxylic acid and relating to 100 mol-% diamine from                a) 65 to 85 mol-%, preferably 67 to 80 mol-%, even more preferably approx. 71 mol-% PACM and        b) 15 to 35 mol-%, preferably 20 to 33 mol-%, even more preferably approx. 29 mol-% MACM.        
It is also beneficial if the at least one polyamide and/or polyamide blends formed from MACM, PACM and/or HMDA as well as IPS and/or TPS as well as lactams and/or α-/ω-amino acids, if necessary. Furthermore, it is also preferred if the at least one polyamide and/or polyamide blends are formed relating to 100 mol-% diamine from 15 to 60 mol-%, preferably 15 to 55 mol-%, even more preferably 25 to 50 mol-%, most preferably approx. 29 mol-% MACM and 40 to 85 mol-%, preferably 45 to 85 mol-%, even more preferably 50 to 75 mol-%, most preferably approx. 71 mol-% HMDA and 0 to 20 mol-%, preferably 0 to 15 mol-%, even more preferably 0 to 10 mol-% PACM as well as relating to 100 mol-% of the dicarboxylic acids from 40 to 60 mol-%, preferably 45 to 55 mol-%, even more preferably approx. 50 mol-% IPS and 40 to 60 mol-%, preferably 45 to 55 mol-%, even more preferably approx. 50 mol-% TPS.
Another advantageous embodiment provides that the at least one polyamide and/or polyamide blends thereof is formed relating to 100 mol-% diamine from approx. 39 mol-% MACM and approx. 52 mol-% HMDA and approx. 9 mol-% PACM as well as relating to 100 mol-% of the dicarboxylic acids from approx. 50 mol-% IPS and approx. 50 mol-% TPS.
In particular, these embodiments provide that up to 10 wt.-%, preferably 0.5 to 10 wt.-%, even more preferably 0.5 to 8 wt.-%, most preferably 0.5 to 6 wt.-% with respect to the total weight of the polyamide molding material is formed from a lactam and/or an α-/ω-amino acid.
In a special embodiment, approx. 4.6 wt.-% with respect to the total weight of the polyamide molding material is formed from a lactam and/or an α-/ω-amino acid.
In another special embodiment, approx. 3 wt.-% with respect to the total weight of the polyamide molding material is formed from a lactam and/or an α-/ω-amino acid.
Advantageously, the lactam and/or the α-/ω- amino acid is LC 11, LC 12, α-/ω- amino undecane acid and/or α-/ω- amino dodecane acid.
Embodiments, in which the at least one polyamide and/or polyamide blends have equal portions of IPS and TPS, are particularly preferred.
Moreover, the invention includes an advantageous alternative embodiment, in which the at least one polyamide and/or polyamide blends is formed from HMDA as well as IPS and/or TPS. It is thereby preferred if the at least one polyamide and/or polyamide blends are made of approx. 100 mol-% HMDA as diamine and relating to 100 mol-% dicarboxylic acid from                a) 60 to 75 mol-%, preferably 62 to 70 mol-%, even more preferably approx. 66.7 mol-% IPS and        b) 25 to 40 mol-%, preferably 30 to 38 mol-%, even more preferably approx. 33.3 mol-TPS.        
In the case of the previously named molds, the dicarboxylic acids can be replaced up to a maximum of half of their molar content with naphthalene dicarboxylic acid, preferably with 2,6 naphthalene dicarboxylic acid.
In the case of the aforementioned formulations, the content of dicarboxylic acid and/or the content of diamines can also be slightly larger or smaller than 100 mol-%. Slightly should be understood to mean a deviation of +/−5 mol-%.
The molds according to the invention are characterized by excellent optical and mechanical properties. The mold preferably has light transmission of at least 88%, preferably at least 90%, even more preferably at least 91%, most preferably at least 92% with a layer thickness of 2 mm, measured based on ASTM 1003. Furthermore, the preferred alternating bend resistance with fixation is at least 75,000 measurement cycles, even more preferably at least 100,000 measurement cycles, most preferably at least 140,000 measurement cycles measured as per ISO 178 with a special test piece (as described below in the examples).
In particular, the molds according to the invention are characterized by a refractive index of 1.490-1.75, preferably 1.550-1.75, even more preferably 1.570-1.75. Another advantageous characteristic of the mold is an Abbe number of at least 25, preferably at least 27, even more preferably at least 28. The mold can also be colored. The mold can also have an optically active coating and/or a protective coating.
Furthermore, the mold can contain the additives known to the person skilled in the art for setting desired properties. In particular, the additives are thereby selected from the group consisting of condensation catalysts, chain regulators, defoaming agents, stabilizers, lubricants, dyes, photochrome additives, antistatics, demolding agents, optical brighteners, natural phyllo silicates, synthetic phyllo silicates or mixtures of the named additives.
In particular, the transparent mold according to the invention is an optical mold. An optical mold is a mold that has an interaction, e.g. absorbing, breaking, dispersing, reflecting interaction, with electromagnetic radiation with a wavelength in the range of 180 nm-1200 nm. Optical molds are also molds that are used in e.g. optical instruments or optical systems.
Transparent molds with a high rigidity, high chemical resistance, high dynamic load capacity and a high stress fracture resistance and higher heat resistance can also be made available with the aforementioned molds.
These properties simultaneously fulfill the high requirements of filter cups in domestic or commercial drinking water systems or compressed air systems, in which a lot of pressure-swell cycles with a high bursting strength must be managed as a result of abrupt pressure changes.
The molds according to the invention are also suitable for applications with high dynamic load capacity and high chemical resistance, in particular for corrective lenses, non-corrective lenses, lenses for frameless glasses, frameless glasses, glasses frames, sunglasses, corrective glasses, safety glasses, ski glasses, motorcycle glasses, protective glasses, visors, helmet visors, coverings, viewing glasses, protective shields, protector caps, camera lenses, magnifying glasses, prisms, automotive coverings, mirrors, flow meters, filter cups, diving computers, watch housings, mobile phone housings and displays, monitor coatings, polarization coatings, containers, fat containers, packaging, automotive windshields, light conductors, light conductor parts, lamp shades, decorative objects and other transparent parts that require these properties.
The molds according to the invention are also suitable for applications with high dynamic load capacity and high chemical resistance and high hardness, in particular for rodent-resistant tubes, lines, casing for electrical cables, film hinges, protective films, cable binders, connectors, optical light conductors.
The polyamide molding materials for the molds according to the invention are also suitable for the production of molds in which the weakening of the material structure comes from e.g. joint lines or welded seams.